Machine for making absorbent sanitary articles

ABSTRACT

Described is a machine for making absorbent sanitary articles, such as nappies, sanitary pads and the like, where each article ( 2 ) comprises a plurality of components ( 8,9 ) progressively positioned relative to each other and assembled along a production line ( 3 ) through a plurality of operating stations ( 24,25,26,27,28,29,32,35 ) equipped with devices for cutting and/or sealing the materials the articles ( 2 ) are made up of and at least one rejection station ( 39 ) downstream of the operating stations; the machine ( 1 ) comprises a programmable electronic controller device ( 42 ) having a shift register ( 40 ), at least one optical inspection system ( 36 ) connected to the programmable electronic controller device ( 42 ), and an operator interface ( 51 ) connected to the electronic controller ( 42 ); the programmable electronic controller device ( 42 ) generates a machine ( 1 ) sync signal ( 43 ), a trigger signal ( 46 ) for activating the optical inspection system ( 36 ) in phase with the sync signal ( 43 ) and a shift register ( 40 ) shift command ( 47 ); the optical inspection system ( 36 ) receives the trigger signal ( 46 ) and has a defined maximum response time (T) which produces at least one band of uncertainty ( 48 ); the operator sets with the operator interface ( 51 ) the instant of activating the shift register ( 40 ) shift command ( 47 ) outside the band of uncertainty ( 48 ) and between two consecutive sync signals ( 43 ) defining a machine step ( 45 ).

TECHNICAL FIELD

This invention relates to a machine for making absorbent sanitaryarticles.

More specifically, the invention relates to a machine for makingabsorbent sanitary articles such as nappies for children and adults,sanitary pads and the like.

BACKGROUND ART

As is known, a machine for making absorbent sanitary articles has aproduction line along which advances a continuous web of absorbentmaterial consisting of a layer of permeable material (of non-wovenfabric) laid over a layer of impermeable material, with absorbentpadding interposed between the two layers. As the continuous webadvances along the production line, additional components are applied tothe continuous web, such as, for example, lateral stretch bands. lateralsealing flaps, a rear stretch tape and a front band designed to engagethe lateral sealing flaps.

Once these additional components have been applied to the continuousweb, a continuous succession of absorbent sanitary articles is formedand a cutting device located downstream of the production line dividesthe continuous succession into individual absorbent articles which arethen folded and packed.

Every line for the production of absorbent sanitary articles alsocomprises at least one rejection station, located downstream of thecutting device, which rejects the defective absorbent sanitary articles,that is to say, the absorbent articles which do not meet specifiedquality parameters.

Checking for defective absorbent sanitary articles is carried out by asoftware logic built into an electronic controller of the makingmachine.

The machine controller, besides generating a machine sync signal 100, isdesigned to assign information about the article being processed to ashift register 101, as illustrated in FIG. 1. The shift register 101 isdefined by a plurality of steps 102, each associated with a timeposition of an absorbent article being processed along the productionline.

In order to identify the defective absorbent articles, the productionline comprises a plurality of check points for checking that theabsorbent sanitary article has been made up correctly. These checkpoints are connected to the machine controller and are designed todetect and flag any production defects in each absorbent article beingmade.

The moment a check point detects and flags a production defect to themachine controller, the latter assigns that information item to aparticular step 102 of the shift register 101. The step 102 is shiftedalong the shift register until reaching a last position 108corresponding to the rejection station where the defective absorbentsanitary article is rejected.

At the check points, generally speaking, there are optical inspectionsystems, such as photocells, or vision systems comprising, for example,commercial video cameras.

A photocell is an inspection component which generates a random signal103 which is asynchronous relative to the machine sync signal 100. Theasynchronous signal 103 of the photocell is defined as ambiguous 104when it is concurrent with the machine sync signal 100 and unambiguous105 when it is not concurrent with the machine sync signal 100.

If the photocell signal is unambiguous 105, relative to the machine syncsignal 100, the machine controller assigns the defective articleinformation item to a particular step 102 of the shift register 101, sothat the defective absorbent sanitary article is certain to be rejectedwhen it reaches the rejection station.

If the photocell signal is ambiguous 104, relative to the machine syncsignal 100, an uncertainty window is created and the machine controlleris unable to assign the defective article information item to aparticular step 102 of the shift register 101. In this case, the machinecontroller assigns the information item to two or more steps 102 of theshift register 101 in order for the defective absorbent sanitary articleto be certainly identified and rejected. Unfortunately, however, thatmeans that absorbent sanitary articles which are not defective arerejected together with the defective article at the rejection station.

From the above, it may be inferred that every time the photocell signalis ambiguous 104 relative to the machine sync signal 100, a significantquantity of good products are rejected together with the defectiveproducts, which translates as a considerable waste of raw materials.

Unlike photocells, vision systems are stable response systems since theyare controlled by a trigger pulse 106 generated by the machinecontroller.

From the moment the vision system receives the trigger pulse 106, it hasa maximum response time to flag a defect, if any, thus defining a bandof uncertainty 107 which may be concurrent with the machine sync signal100 and hence ambiguous. as illustrated in FIG. 1. Under theseconditions, the machine controller is unable to determine a specificstep 102 of the shift register 101 to assign the defective articleinformation item to and, as in the case of the ambiguous photocellsignal 104, assigns the information item to two or more steps 102 of theshift register 101 so that the defective absorbent sanitary article iscertainly identified and rejected.

Even the use of a vision system does not solve the problem of rejectingsanitary articles which are not defective. Thus, every time the band ofuncertainty 107 is ambiguous relative to the machine sync signal 100 aconsiderable number of good products are rejected together with thedefective products.

DISCLOSURE OF THE INVENTION

The aim of this invention is to provide a machine for making absorbentsanitary articles and which rejects only the defective product, withouthaving to reject any products which are not defective, thus minimizingthe number of products which, the machine must strictly reject.

The above mentioned technical purpose and aims are achieved by a machinehaving the technical features described in the independent claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of this invention are more apparent inthe description below, with reference to a preferred, non-limiting,embodiment of a machine as illustrated in the accompanying drawings, inwhich:

FIG. 1 illustrates control signals and information in a prior art makingmachine:

FIG. 2 is a schematic front views of a making machine according to thisinvention:

FIG. 3 illustrates an absorbent sanitary article without productiondefects, made by the machine illustrated in FIG. 2;

FIG. 4 shows the absorbent sanitary article of FIG. 3 with someproduction defects;

FIG. 5 is a block diagram representing the inspection section of themachine of FIG. 2;

FIG. 6 shows a series of control and checking signals generated by theinspection section of FIG. 5;

FIG. 7 shows a first variant of FIG. 6;

FIG. 8 shows a second variant of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

As shown in FIG. 2, the numeral 1 denotes a machine for making absorbentsanitary articles 2 and comprising a substantially horizontal productionline 3 along which the absorbent sanitary article 2 is made.

The article 2 has a substantially rectangular shape and comprises, in aline along its longitudinal axis A, a front portion 4, a central portion5 and a rear portion 6, as illustrated in FIG. 3.

At the central portion 5 the article 2 has a recess 7, or thigh opening,defined by two arcuate sections which are symmetrical about the axis A.

The articles 2 are composed of a plurality of components, which can bebroadly divided into main components 8, or basic parts, and accessorycomponents 9, or accessory parts.

The main components 8 include a sheet 10 of impermeable material and asheet 11 of permeable material (non-woven fabric) used to make theoutside face and the inside face of the article 2, respectively.

The sheets 10 and 11 are laid over each other and interposed betweenthem there is another main component constituted by an absorbent padding12.

The accessory components 9, which may vary in number and shape, aredescribed below with reference to the sanitary article 2 illustrated inFIG. 3.

The numeral 13 denotes two shaped flaps fixed to the inside face of thesheet 10 and extending from the front portion 4 transversely to the axisA.

The numeral 14 denotes two shaped flaps, parallel to the flaps 13,extending from the rear portion 6.

Applied to each of the flaps 14 there is a tab 15 provided with anadhesive strip 16 designed to adhere, in use, to a corresponding frontstrip 17 applied to the front portion 4 of the outside face of the sheet10.

Laterally sealed to the sheet 11 of permeable material there are twostrips 18 of impermeable material for thickening and expanding itslongitudinal edges.

A further accessory component 9 is a stretch tape 19 appliedtransversely of the axis A to the inside face of the rear portion 6 ofthe sheet 10.

With reference to FIG. 2, the machine 1 comprises a base 20substantially in the shape of a parallelepiped and delimited at thefront by a vertical wall 21.

The wall 21 constitutes a support for a plurality of operating units.These operating units comprise cutting devices and sealing devices, aswell as units for unwinding the materials making up the article 2 fromrespective rolls mounted on axes transversal to the wall 21.

The making machine 1 is a cyclic production machine of continuous type,that is to say, at each machine cycle, one finished absorbent sanitaryarticle 2 is made.

At its infeed, the machine 1 comprises a unit 22 for unwinding acontinuous web 23 of impermeable material which, after being cut intolengths, constitutes the sheets 10.

The continuous web 23 runs along a horizontal path P of the productionline 3, in the direction indicated by the arrow F, through the operatingunits where the article 2 is progressively made up and completed bysuccessively adding the basic components 8 and the accessory components9,

At a first operating unit 24, the front strip 17 transversal to the axisA is applied in known manner, using an adhesive substance, to the frontportion of the outside face of each length of the of the web 23corresponding to an absorbent article 2.

At a second operating unit 25, the tape 19 of stretch material isapplied transversely to the axis A in known manner, using an adhesivesubstance, to the rear portion of the inside face of each length of theof the web 23 corresponding to an absorbent article 2.

At a third operating unit 26, the absorbent padding 12 is applied to thecentral zone of each length of the web 23.

Downstream of the operating unit 26 the web 23 passes through a fourthoperating unit 27 where the two front flaps 13 are made and henceapplied to each length of the web 23.

Downstream of the operating unit 27, along the path P, there is a fifthoperating unit 28 where the two rear flaps 14, each of which is providedwith a respective grip tab 15, are made and applied to the web 23.

Downstream of the unit 28, the wall 21 supports, in proximity of itsright-hand end, a sixth operating unit 29 comprising a unit 30 forunwinding a web 31 of permeable material.

At a sealing station 32, the web 31 of permeable material and the web 23of impermeable material are sealed to each other along the respectiveedges to make a continuous web 33 which will eventually define thearticles 2. In other words, the continuous web 33 is a continuoussuccession of finished articles 2 complete with the basic parts 8 andthe accessory parts 9.

The continuous web 33 passes through a further operating unit 34, whereeach length of the web 33 is cut in such a way as to make twosubstantially semicircular portions that will constitute the recesses 7of the absorbent article 2.

Downstream of the operating unit 34, a cutting device 35 transverselydivides the web 33 into the individual finished articles 2.

At the end of the production line 3, downstream of the cutting device35, there is at least one rejection station 39 for rejecting absorbentarticles 2 which are defective. The rejection station 39 is locateddownstream of the cutting device 35. That means the rejection station 39may be located upstream or downstream of a folding station, notillustrated, where each single absorbent article 2 is folded,

The making machine 1 comprises at least one optical inspection system 36for checking the quality of the articles 2 as they feed out of theproduction line 3.

The optical inspection system 36 is designed to detect and flagproduction defects in the finished absorbent article 2.

The optical inspection system 36 comprises at least a video camera 37for capturing at least one image 54 of the absorbent article 2 and aunit 38 for acquiring and processing images of the absorbent article 2and connected to the video camera 37.

In the preferred embodiment, the image capturing video camera 37 is alinear video camera. Further, the optical inspection system 36 is avision system.

More specifically, at least one video camera 37 is located at theoutfeed of the production line 3. In effect, the video camera 37 locatedat the end of the production line 3 inspects the absorbent article 2complete with the basic components 8 and the accessory components 9.

As illustrated in FIG. 2, video camera 37 is mounted to face thecontinuous web 33 of articles 2 while they are still joined to eachother, upstream of the cutting device 35, so as to capture at least oneimage 54 of each article 2 before the latter is cut off from thecontinuous web 33.

As the continuous web 33 advances along the path P, the linear videocamera 37 inspects the web 33 with a field of vision spanning the fullwidth of the web 33.

Alternatively, the video 37 night be located downstream of the cuttingdevice 35 in order to capture at least one image 54 of a single finishedarticle 2 after it has been cut off from the continuous web 33.

The image acquisition and processing unit 38 analyses the images andthereby assesses whether the predefined quality parameters of theabsorbent article 2 fail within respective tolerance ranges. If one ormore of the quality parameters are outside the respective tolerancerange, the acquisition and processing unit 38 flags the presence of aproduction defect in the absorbent article 2.

Production defects or faults, examples of which are given below, mayoccur during the application and forming of the base parts 8 andaccessory parts 9.

FIG. 4 shows some of the components of the absorbent article 2positioned incorrectly. as indicated by the dashed lines, compared tothe correct positions indicated by the solid lines, such as for example,the incorrectly oriented front strip 17 and stretch tape 19, theincorrectly positioned the flaps 13 and 14 and the incorrectly shapedrecess 7.

These production defects, once detected and flagged by the acquisitionand processing unit 38 cause the finished absorbent article 2 to berejected when it reaches the rejection station 39 of the production line3.

Another example of a production defect which causes the article 2 to berejected is the absence of one or more basic parts 8 and/or accessoryparts 9.

In terms of logical representation, the making machine 1 is mapped by asingle shift register 40, as illustrated in FIG. 5.

The shift register 40 or “chain” is represented as a set ofinterconnected rectangular blocks. Each block 41 of the register 40 isdefined as a step of the “chain”.

Each step 41 of the shift register 40 corresponds to time position ofthe absorbent article 2 being made up as it passes through each of theoperating stations of the machine 1. More specifically, the informationrelating to the state of the product or of the material being processedalong the production line 3 is stored in the shift register 40.

The making machine 1 is equipped with a programmable electronic machinecontroller device 42.

The electronic controller 42 applies a shift command 47 to the shiftregister 40.

The shift command 47 shifts each step 41 in a single direction untilreaching the last block 41 b of the “chain” corresponding to the momentthe finished absorbent article 2 is at the rejection station 39.

The electronic controller 42 generates a machine sync signal 43. Morespecifically. the machine sync signal 43 is generated by an encoder.

The sync signal 43 has a train of control pulses 44 with a phase, aduration and a number of repetitions which depends on the process cycleof the machine 1.

More specifically, two consecutive pulses 44 of the sync signal 43define a machine step 45 which corresponds to one position of theabsorbent article 2 being, made up along the production line 3.

The vision system 36 is connected to tt e programmable electroniccontroller device 42.

More specifically, the vision system 36 is activated by the programmableelectronic controller device 42 which generates a trigger signal 46 ofthe vision system 36 in phase with the machine sync signal 43.

From the moment it receives the trigger signal 46, the vision system 36has maximum defined response time for flagging the presence of aproduction defect, if any, of the article 2.

The maximum response time T of the vision system 36 creates a band ofuncertainty 48, or uncertainty window, defined temporally from theinstant in which the vision system 36 receives the trigger signal 46 tothe instant in which the vision system flags the defect, if any.

The duration of the band of uncertainty 48 is a known time quantity,since the maximum response time T is strictly dependent on thetechnology implemented in the vision system 36 itself, both by the videocamera 37 and by the image acquisition and processing unit 38. Morespecifically, based on current technology, the band of uncertainty mayhave a duration of up to 4 msec.

Before the end of the band of uncertainty 48, the image acquisition andprocessing unit 38 sends a rejection signal 49 to the electroniccontroller 42. After receiving the rejection signal 49, the electroniccontroller 42 produces a rejection information item 50 to be assigned toa particular step 41 of the shift register 40. This step, labelled 41 a,is shifted to the last block 41 b of the register 40 in such a way as togenerate a command 55 for rejecting the finished absorbent article 2which is at the rejection station 39.

The vision system 36 inspects one or more areas of each length of theweb 33 corresponding to a complete article 2. For example, the visionsystem 36 inspects the front portion 4 at the front strip 17 and flaps13, the central portion 5 at the recesses 7 and the rear portion 6 atthe flaps 14.

In this case, the vision system 36 generates three distinct bands ofuncertainty 48, each associated with the defects of the respectiveportion 4, 5 and 6 of the article 2.

In order to inspect the chosen areas of the article 2, the vision system36 may use a single video camera 37 or a plurality of video cameras 37,each dedicated to an inspection area. In this specific case, threedistinct video cameras 37 are used, each dedicated to inspecting therespective portion 4, 5 or 6. In an alternative embodiment, each videocamera 37 is dedicated to the optical inspection of certain basic parts8 and/or accessory parts 9 at a certain position along the productionline 3.

More specifically, if the vision system 36 comprises a plurality ofvideo cameras 37, these are activated within the same machine step 45,each generating a band of uncertainty 48.

If the vision system 36 comprises a single video camera 37, on the otherhand, the camera is activated at least once within the same machine step45. generating a respective band of uncertainty 48 associated with thecorresponding activation.

Consequently, one machine step 45 defined by two consecutive sync pulses44 has at least one band of uncertainty 48.

In order to prevent the bands of uncertainty 48 from being concurrentwith the shift register 40 shift command 47, the operator sets with anoperator interface 51 connected to the electronic controller 42, theinstant of activating the shift register 40 shift command 47 within amachine step 45, outside the band/bands of uncertainty 48, asillustrated in FIG. 6.

That way, the shift register 40 shifts either before or after theband/bands of uncertainty 48 so that the step 41 a of the shift register40 which the article 2 defective information item must be assigned to iscertain.

The operator interface 51, comprising a touch screen or a screenkeyboard, is normally implemented by a dedicated software program.

As illustrated in FIG. 7, the operator sets with the operator interface51 the activation of the shift register 40 shift command 47 before theband of uncertainty 48, so that the shift register 40 shifts one step 41before the vision system 36 is activated. After the band of uncertainty48 has elapsed and the defect has been flagged by the vision system 36,the electronic controller 42 assigns the rejection information item 50to the corresponding step 52 of the register 40.

Alternatively, as illustrated in FIG. 8, the operator sets theactivation of the shift register 40 shift command 47 after the band ofuncertainty 48. In this case, the register 40 shifts one step 41 afterthe band of uncertainty 48 has elapsed and the electronic controller 42assigns the rejection information item 50 to the corresponding step 53of the register 40, after the step 52.

In both the cases of FIG. 7 and FIG. 8, only the defective absorbentarticle 2 is rejected at the rejection station 39 because the electroniccontroller 42 is able to assign the rejection information item 50 to asingle step 52 or 53, since unlike the prior art, the shift command 47is not concurrent with the band of uncertainty 48 of the vision system36.

The operation of setting with the operator interface 51 the activationof the shift command 47 outside the band of uncertainty 48 isadvantageous because it allows a single defective article 2 to herejected even when the size of the absorbent articles 2 to be made isvaried.

Indeed, the operator can set up the vision system 36 in such a way as toinspect certain areas of the absorbent article 2, according to the sizeof the article and the quality parameters to be met.

This setup operation involves setting with the operator interface 51 thetrigger signals 46 of the vision system 36.

For example, in a machine 1 which makes 800 absorbent articles 2 perminute, the absorbent article 2 is 400 mm long and the operator, usingthe interface 51, sets the system so it inspects the areas of thearticle 2 at 100, 200 and 300 mm from a predetermined point 0, ororigin, in order to check the basic parts 8 and/or the accessory parts 9in those areas. Considering that the band of uncertainty 48 associatedwith each area inspected blacks out approximately 25 mm of the absorbentarticle 2, the operator can set the shift command 47 so it is activatedeither before or after all the bands of uncertainty 48.

Advantageously, the possibility of setting the activation of the shiftregister 40 shift command 47 not only guarantees that only the defectivearticle 2 is rejected, without having to reject articles 2 which are notdefective, but also allows the making machine 1 to be set up accordingto the size of the absorbent article 2. Setting up that way means thatrejecting only the defective article 2 is possible for absorbentarticles 2 of all sizes. differing in dimensions and possibly also intheir accessory components 9.

1. A machine for making absorbent sanitary articles, such as nappies,sanitary pads and the like, each article comprising a plurality ofcomponents progressively positioned relative to each other and assembledalong a production line which comprises a plurality of operatingstations equipped with devices for cutting and/or sealing the materialsthe articles are made up of and at least one rejection stationdownstream of the operating stations, the machine comprising aprogrammable electronic controller device comprising a shift register,at least one optical inspection system connected to the programmableelectronic controller device, an operator interface connected to theelectronic controller; the programmable electronic controller devicegenerating a machine sync signal, a trigger signal for activating theoptical inspection system in phase with the sync signal and a shiftregister shift command; the optical inspection system receiving thetrigger signal and having a defined maximum response time which producesat least one band of uncertainty, characterized in that the operatorsets with the operator interface the instant of activating the shiftregister shift command outside the band of uncertainty and between twoconsecutive sync signals defining a machine step.
 2. The machineaccording to claim 1, wherein the operator sets with the operatorinterface the instant of activating the shift register shift commandbefore the band of uncertainty.
 3. The machine according to claim 1,wherein the operator sets with the operator interface the instant ofactivating the shift register shift command after the band ofuncertainty.
 4. The machine according to claim 1, wherein the opticalinspection system comprises at least a video camera for capturing atleast one image of the absorbent article and an image acquisition andprocessing unit connected to the video camera.
 5. The machine accordingto claim 4, wherein the image capturing video camera is a linear videocamera.
 6. The machine according to claim 1, wherein the opticalinspection system is a vision system.
 7. The machine according to claim1, wherein at least one video camera is located in the proximity of theoutfeed end of the production line.
 8. The machine according to claim 1,wherein the video camera is activated at least once within a single stepproducing a corresponding band of uncertainty; the operator setting withthe operator interface the instant of activating the shift commandoutside the band of uncertainty.
 9. The machine according to claim 1,wherein a plurality of video cameras are activated within a single stepeach producing a corresponding band of uncertainty; the operator settingwith the operator interface the instant of activating the shift commandoutside the bands of uncertainty.
 10. A method for making absorbentsanitary articles, comprising a step of generating a machine sync signalthrough the agency of the programmable electronic controller device, astep of sending a trigger signal to an optical inspection system throughthe agency of the programmable electronic controller device, the opticalinspection system having a maximum response time and producing a band ofuncertainty, a step of applying shift command on a shift register of theprogrammable electronic controller device, characterized in that itcomprises a step of setting, with an operator interface connected to theprogrammable electronic controller device, the instant of activating theshift register shift command within a machine step defined by twoconsecutive sync signals and outside the band of uncertainty.